Process for nitrating cellulose



Patented May l5, 1923. p

HENRY V. WALKER, F NEWARK, NEW JERSEY.

PROCESS FOR NITRATING cELLULosE.

Original application filed May 20, 1920, Serial No. 382,810, Dividedand this application led September 23, i922. serial No; 589,961.

To all whom 'it may concem Be it known that I, HENRY V. I VnLKnR, a citizen of .the United States, residing in vNewark, county of Essex, State of New In the manufacture of nitro-cellulose orl gun-cottomthe raw cotton is first subjected to the action of sulphuric. and nitric acids in suitable proportion to produce the necessary nitrating reaction. The excess acid is then removed, o far as possible by inechanical action, an this vprocess is finally completed by a se ies ofpboilin and washing operations to r nder the pro uct thoroughly stable.

It has been common, hitherto, to carry on the nitrating process in the basket of a centrifugal separator, and, after the mixture has stood for a sufficient time to complete the reaction, the Iseparator isset runnin so as to 'accomplish the mechanicalextraction, of the excess free acid. The boilin and washin processes follow this centrifugal extraction process. v

By thus using the centrifugal machine as a dip ing chamber, a good deal of time is lost, cause the machine 1s prevented -from-,carrying out its proper natural function as an extractor during the time occupied by the chemical reaction.. The same waste of time is involved where the dipping is done in 'a separate chamber which is discharged into the waitin centrifugal machine after completion o each reaction.

The present invention involves a process wherein 'a succession of charges of mixed cotton (or equivalent substance) is conveyed in a continuous series by intermittent movements, suitably timed, from a charging point to the point of extraction, and wherein the extracting process on the one hand and the charging process on the other hand are accomplished simultaneously at opposite ends of the moving. series, during` the time intervals ,between the successive forward movements of the charges. It is a novel characteristic of my improved processv that, during the forward movement of the material, it is given a gentle agitation. By .this plan itis clear that a suiiicient time can be given to carry out the nitration of each charge while it is moving forward through the series of allotted positions; while, on the other hand, the extracting machine is kept busy all the time, being emptied after each extraction and placed in readiness for the next charge in the series.

Another important advantage presented by this process is found in the fact that it admits of automatic control of the time of nitration. In prior systems the time of nitration is subject .to the -control of the operatonbut in the present system this is not tlie case as the first charge cannot leave the dipping series until a number (preferably four) subsequent charges have been introduced into ,the series. Suiiicient time for nitratlon is thus insured for every charge. The apparatus forming a part of this in-v vention has the advantage-of great simplicity in construction and operation-particularly in regard to the acid disposition of fumes.

A form of apparatus for carrying out this process is illustrated in the accompanying drawings, wherein Figure 1 is a diagrammatic side elevation, partly in section, of the complete apparatus, Figure K2 is an end View of the nitrating cylinder viewed from the left in Figure 1, Figure 3 is a sectional View of the apparatus on the line`3-3 in 'Figure 1, and Figure 4 is a-.detail view of the discharge end of the nitrating cylinder. The nitrating cylinder 10 is furnished with an internal partition 11 extending in a wide spiral from end to endl of the cylinder. .The outer edge of this spiral or helical artition is closelylunited to the interior of t e cylinder, preferably by welding; and it thus divides the cylinder into four chambers or compartments. Central o enings 12 are formed in the successive spira s, serving both to facilitate construction and to-make it possible to carry oif from all the com art ments the fumes which are normally isen-- gaed during nitration.

t the charging end of the cylinder, a. door 13 is furnished, through which the o erator may introduce the cotton and mix it,

piping, and the by means of an iron fork, with the heated acids which may run in through the piping 14. The discharging end of the cylinder Y is provided with a discharge chute 15.

Suitable. means are employed whereby the cylinder and its internal partitionfmay be revolved upon their common axes; and for this purpose, in the form shown, friction bands 16 and 17 are provided which rest upon friction wheels 18, 19, near each end.

The wheels 19 are fixed to a common driving shaft 20, by means of which they are made to drive the cylinder 10. Any motive means (automatic or otherwise) may be used for driving the shaft 20; as, for instance, an electric motor 21, acting through the belt 22, and clutch 23. This clutch is operated by the handle 24, so that the revoable mechanism, as, for instance, the pneumatic lift 27.

Just beyond the extractor 25 is placed the washing tank 28 for removing the excess free acid from the cotton which leaves the extractor. This is preferably provided with a raised perforated bottom 29, from under which' the water may be drawn off' through the drain 30.

A fume-hood 31 extends over the extractor 25 and over the front end of the tank 28; and fume pipes 32, 33 extend out from under this hood, through which the fumes are drawn od in a well known manner. The motor for driving the centrifugal acid extractor is indicated at 34.

The improved process is carried oufl in this apparatus as follows- 'The heated acids are-,introduced by the operator into the first nitrating compartment, together with the proper quantity of cotton. The charge thus formed fills this charging compartment up to a level somewhat -under'the lower edge of the door 13; through which the operator can manipulate the charge by means of a suitable tool. The mixture being accomplished, the cylinder is rotated through a single revolution and is then stopped. rlhisresults in transferring the entire charge to the second compartment, leaving the' first or charging compartment empty, and ready for a new charge. At the same time, the friction of the rotating walls of the helix serves to promote av mild agitation in the mixture. l y

rlhe operations thus far described are repeated indefinitely, with the result that each charge in succession is finally brought intoA the last compartment, in which, as shown at 35 in Figure 4, the helix is so shaped as to lift the charge to the level of the chute 15, through which it falls by gravity into the removable basket 26 of the centrifugal ex-l` tractor. Y v

Between successive revolutions of the cyl"- inder 10, and therefore between successive deliveries of charges through the chute'15, 7' l, 5 p moval of the basket 26 whose .cont'enfts'fare'l' the extractor 25 is operated, emptied byre'fdumped into the tank 28, and prepared' for a new charge by return of the basket toits Y place. At the same time the first compartment is being charged, as already described.

It will be seen that, by this arrangement, there is a. series of successive charges moving step by step toward the extractor which Y is thus kept always in operation, except during the necessar removal and return'of the inner basket. s each charge has to move through the whole series of positionsbefore being delivered to the extractor, ample time for nitration is provided. rlhis time can be regulatedV by the number of positions and the time it takes to charge and to extract. In practice, it has been found that good results are achieved by the use of four compartments and four positions of rest, but, of course, the invention is not limited to any given number of positions.

What is claimed is- The process of nitrating cotton and the like which comprises the following steps,

namely z-conveying a succession of separate HENRY V. WALKER.

ico 

